The present invention relates to an edible spread and to a processes for producing such a spread.
Butterfat, although possessing a reputation as a "healthy natural" fat contains a high proportion of fats having a relatively low level of unsaturation. Details of the exact composition of butterfat can be found in International Dairy Federation document 125 (pp 4-13). Typical compositions for milk fat are 61% saturated fatty acids, 36% cis mono-unsaturated fatty acids and 3% cis poly-unsaturated (so-called "essential") fatty acids.
In recent years there has been considerable medical interest in reducing the dietary intake of saturated fats. Consumers now find a diet rich in saturated fat unacceptable, and research has long been concerned with how a proportion of the fat may be replaced by vegetable oils, which are accepted to be dietetically more acceptable. In addition, recent years have seen an increasing consumer awareness that the total cholesterol level in the diet should not be too high. This has again contributed to a shift from dairy fat consumption to vegetable fat consumption.
The first margarines were manufactured from animal tallow. Vegetable oils were first added to margarine fat compositions towards the end of the nineteenth century, in proportions of around 20% in order to soften the end product. As the price of animal fats rose, use of vegetable fat increased until by 1907 vegetable fat comprised some 25-30% of the fat blend of European margarines. It was not possible to incorporate more than this proportion as the resulting products became far too soft during warm weather.
In 1912-13 edible hydrogenated fats became available in commercial quantities. Hydrogenation increases the melting point of fats which would otherwise be liquid at ambient temperature and tends to products with a smooth melting curve. With the advent of these harder fats it became possible to produce vegetable fat blends having similar melting properties to animal fats and the margarine industry became relatively independent of the beef fat and lard market. However, partially hydrogenated fats contain a reduced level of cis-unsaturated fatty acids and fully hydrogenated fats contain exclusively saturated fats. These chemically modified fats are considered less acceptable than unmodified vegetable fats. Moreover, hydrogenation and other modifications of edible fats require expensive catalysts and a considerable investment in plant and workforce.
The properties of fats may also be modified by fractionation, with or without solvents. One difficulty of fractionation is that many separations result in fat fractions with limited usefulness.
In addition to the overall fatty acid content of fats, the stereochemistry of triacyl-glycerols and the effect of this upon the physical properties of the fat and spreads containing these fats has been investigated. As a result, interesterification, carried out in the presence of catalysts has been used to modify the physical properties of fats. This has resulted in fatty materials which enable spreads to be made with low levels of saturated fats. Interesterification is a complex, expensive processing step and requires the use of expensive enzyme catalysts if side reactions are to be minimised.
In considering this prior art it is convenient to use the notation given in table 1, as used throughout this specification:
TABLE 1 ______________________________________ FATTY ACID NOTATION ______________________________________ S stearic acid, (C18 saturated) P palmitic acid, (C16 saturated) M lauric fats, (C12-C14 fats) H stearic + palmitic (C16-C18 saturated) O oleic acid, (C18 cis unsaturated) L linoleic acid, (C18 cis cis diunsaturated) E mono-trans fat, and (C16-C18 mono trans) U oleic + linoleic. (C16-C18 unsaturated) ______________________________________
It should be noted that the "E" fats occur in nature only in very low concentrations: trans carbon-carbon linkages are generally only found in chemically hydrogenated fats.
U.S. Pat. No. 4,267,643 discloses some of the S2E and SES ratios which can be obtained by non-fractionated but hydrogenated vegetable oils.
JP 54/034305 and JP 52/069411 disclose specific S2U, SU2, S3 and U3 ratios obtained by mixing of co-randomised vegetable fats.
The effect of S20 fats on physical properties of a fat is discussed in EP 78568 and U.S. Pat. No. 4,447,462. The effect of S2U fats on physical properties is discussed in EP 109721.
In general the prior art indicates that the symmetric HUH triglyceride is preferable to the HHU triglyceride. Fat blends comprising plurality of components obtained from differing sources or requiring extensive, and expensive, modification of part or all of the fats present have been suggested as a source of this material.
As well as hydrogenation, fractionation and interesterification, saponification has been proposed as a suitable modification of fats, so as to stabilize spreads containing vegetable fats. For example in U.S. Pat. No. 3,026,207, over 5% of a soap is added to a fat to stabilize a water and oil emulsion. As is well known, soap is traditionally a chemically modified fat.
Despite over a century of research, workers have been unable to produce an edible spread which, like butter, comprises a single vegetable fat which has not been subjected to modification.